Servo-anemometer device



2 Sheets-Sheet 2 E. F. G. GARNIER SERVO ANEMOMETER DEVICE Jan. 9, 1951Filed March 3, 1948 Patented Jan. 9, 1951 "SERVO-ANEMOMETER DEVICEEugene Francois Gilbert Garnier, Nice, Alpes Maritimes, FranceApplication March 3, 1948, Serial No. 12,818

In France June '15,- 1943 1 a 3 Claims.

The present invention relates to improvements in devices used forindicating the aerodynamical speed in aircrafts.

It relates more particularly to devices of such type, .wherein theindications are made concurrently in response to the difference betweenthe aerodynamic pressure and the surrounding static pressure, the valueof said surrounding static pressureand the value of the absolutetemperature of the surrounding atmosphere.

Devices of the above defined type have already been constructed, suchdevices being sometimes known as servo-anemometers, and wherein thereare arranged serially along a circuit adapted to receive through atiming switch, electric timing pulses, the cycle duration of which is afunction of a variable quantity N, three periodic switches, theactuation of which is controlled through devices adapted respectively toact in response to the square roots of the difference A between theaerodynamic pressure and the static pressure of the surrounding medium,the value P of said surrounding static pre:sure and the value T of theabsolute temperature of the surrounding air, in such a way that thenumber of pulses transmitted per unit time through said periodicswitches, will be a function of /A,

and of VT, the resulting pulses being registered in appropriatetotalizer, whereby the movable indicating member of the latter will besubjected to a displacement at a rate which is a function of theproduct:

In such an arrangement, the series of pulses transmitted presents gapsof more or less long duration which, while not presenting any drawbackswhen it is desired to actuate a device of the totalizer type, are notpermissible in the event the servo-anemometer is to be associated withan instantaneous speed indicator, as is considered to be essential incurrent aircraft navigation, especially because the continual increasesin the speed and altitude of the aircraft result in greater and greatervariations in the factors A, P and T and, as a consequence, thediscontinuous character of the operation of the device tends to becomeamplified.

Moreover, the increase in the actual speed of aircraft is such that itis no longer possible to 2 consider A as being proportional with thesquare of the speed. Rather, A should be considered as being expressedby a formula of the following form: Y

Plotting the curve representing this function with the values of l orreversely:

in abscissae and the values of V along the ordinates, and rotating saidcurve about the abscissa axis at a constant angular rate, there isobtained a solid of revolution each point M of which moves at a speedproportionate to V if its abscissa is proportionate to A The main objectof this invention is to provide, in a servo-anemometer, means adapted tocompensate for or cancel out the effects of discontinuity andirregularity in the series of resulting pulses. t a.

Another object of the invention is to provide, in a servo-anemometer ofthe character de-% scribed, means for varying the frequency of thetiming pulses in proportion to the variations of a function of thefraction 1 A further object ofthe invention is to provide,

in a servo-anemometer of the character de scribed, a timing switchdriven in rotation by at least one member adapted at any time to betangent to a point of a surface of revolution of the above definedcharacter generated as described by the representative curve of thefunction of at least two variables.

Still another object of the invention is to provide, in aservo-anemometer of the character de-=' scribed, two means, one'ofwhichis tangent to a surface of revolution, the generatrix of whichrepresents a function of T, and the other one to a surface-oirevmutionrepresentative of a function of the fraction the variations of whichfraction are of lesser amplitude than those of each of its terms takenseparately, since both said terms essentially vary in the same directionto each other.

Yet another object of the invention is to provide, in a servo-anemometerof the character described, means for converting the indication of thevariations of the ratio between two variables into an indication of thevariations of the tangent of an angle variable as a function of bothsaid variables.

The ensuing description, made in reference to the accompanying drawings,given merely by way of indication and not of limitation, will clearlyshow in what way the invention may be put into practice. In thedrawings:

Fig. l is a curve representative of the function:

'1 Fig. 2 is an explanatory diagram illustrating the opertationof animproved device according to the invention adapted to translate orconvert into mechanical operations the variations of the ratio tan 5:

I .Referring to Fig. 1, there isillustrated the representative curve foraerodynamic speed in an aircraft as a function of the difference Abetween the aerodynamic pressure and the static pressure of thesurrounding medium, the value P of said sur ounding static pressure andthe value T of the absolute temperature of the surrounding air, whereinthe values of V are plotted against the values of v In some casesencountered in present practice, a sufiicient approximation is given byassuming that the function between the aerodynamic speed and the threeabove defined variables is of the form:

To mechanically translate the variations of the ratio for instance, itis convenient to use the geometric feature illustrated in Fig. 2.

In this figure, AB is a straight line which may be displaced so as toremain parallel to a constant direction, 0 is a fixed point contained inthe III:

4 plane of displacement of the line AB, OM is a straight line issuedfrom O and extending through a point M movable along the line AB, M0designates the foot of the perpendicular line from O to the line AB.Assuming the displacements of AB and of the point M to be so correlatedthat at any given instant 0M0 will be proportional to P and MMo will beproportional to A, it will be seen that the tangent of the angle MoOMequals The above property is used in the device illustrated in Fig. 3,in order to obtain a transmission of electric pulses at a pulsingfrequency which is a function of As shown in -Fig. 3, there is mountedupon a frame structure, not shown, the fixed end of a manometric capsuleI30, the movable end I3I of which is suitably formed so as to serve as aguide for a slide block I32 movable in a direction at right angles tothe axis of the capsule I30. Opposite to the movable end I3I of themanometric capsule, a lever I34 is mounted so as to be pivotable aboutan axis I33 perpendicular to the plane defined by the center axis of thecapsule I30 and the direction of displacement of the slide block I32.Said lever I34 is maintained for instance through a spiral spring I35 incontact engagement with a projection I36 of the slide block I32.

The slide block i132 at one of its ends comprises an arm I40 forming a'i, the outer side face of which is substantially parallel with the axisof the manometer capsu.e I30. Said outer face of the arm In of the slideblock I32 is at all times applied for instance by the action of a spring-I III against the follower roller I4I provided at the end of one of thearms of a bell-crank lever I42 pivoted on an axis I43. The other arm ofthe lever I42 is connected with the movable end of a barometer capsuleI44, the opposite end of which is secured to the frame, not shown, ofthe device. If the manometer capsule I30 is so arranged as to measurethe amount A, while the barometer capsule is arranged to measure theamount P, it will be seen that the tangent of the angle formed betweenthe lever I34 and the direction of displacement of the slide block I32is equal to The above described device shown in Fig. 3 further makes itpossible to obtain a multiplication by the factor /I by means of adevice adapted to modify the pulse frequency of the pulses transmittedat function of VT. For this purpose, a shaft I50, driven in rotation ata rate which is the function of through drive means to be describedhereinafter,

flange I15 so that the roller I52 is constantly maintained in contactwith the surface of the drum Iol in the sliding movements of the latteralong the shaft I50. The shaft I53 has keyed thereon the rotor memberI54 of the rotary switch, the brushes I55 and I56 of whichsimultaneously engage one or more conductive strip elements I51 of equalwidth provided at the periphery of the rotor I54. The brushes I55 and155 are connected in series in an electric pulse generating circuitconnected with an utilization apparatus D receiving the indication ofthe speed of shaft I 53 by means of successive impulses emitted by therotary switch. The drum I5I is formed witlran angular groove I58 intowhich project fingers or lugs provided at the end of the arm of thefork-shaped lever I59 pivoted at its opposite'end on'apivotal axis I60.The oscillations of said lever about its axis I60, are controlled from athermostatic strip I06 secured as at I01 to the frame of the device, insuch a waythat the sliding displacements of the drum I5I along the shaftI50 will be a function of the absolute temperature T. If further asuitable longitudinal contour is imparted to the drum it will be seenthat the speed of rotationof the roller I 52 and consequently of therotary switch secured on the shaft I53 of said roller may be made tovary as a function of VT, whereby the number of pulses generated by therotary switch per unit time, will also be a funtion of VT, assuming Aand P to remain constant.

For the purpose of effecting a multiplication by a cam and followerroller arrangement is used which is similar to the one just described inconnection with multiplication by x/T. However, since multiplication byrectly connecting it with the lever I34 subjected to the variations ofAs shown, a suitable motor I through a pinion I1I secured on its driveshaft, drives'a gear I12 secured on a shaft I13 journalled at both endsin fixed flanges I14 and I15. The shaft I13 has secured thereon, a camI16 and the speed of the shaft I13 is held at a strictly constant valueby any suitable means, such as a conventional clockwork escapementmechanism I02 adapted to control the speed of a shaft I19 operativelyconnected with the shaft I13 through gears I11 and I18.

A suitable follower roller I80 is maintained applied against theperiphery of the cam I16. The roller I80 is slidable along a shaft I8Iwith which it is connected in rotation. The shaft I8I is journalled atits ends in a support I 82 and drives the shaft I50 by means of a pinionI83 secured on the shaft I8 I, a freely rotatable gear I 84 meshing withsaid pinion I 83 and a pinion I85 secured on the shaft I50.

The displacements of the follower roller I80 along its shaft I8I areeffected in the following manner: the hubof the roller I80 is arrangedbetween the prongs of a fork I86, the body portion I81 of which isadapted to form a nonrotatablenut threaded on a screw I88 journalled atboth ends thereof upon the support I82, the flange I15 and the flangeI89. The support I82 is rockable around the screw I88 and is resilientlyurged by the action of the spring I83 connected with the flange I15 forinstance in such a manner that the follower roller I80 is always incontact with the cam I16. The screw I88 at one of its ends rigidlysupports a pinion IIO meshing with the pinion I90 secured on a shaft I9Ijournalled at one of its ends in a suitable aperture formed in theflange I15 and at its opposite end in a bearing I82 secured at one endof a rod I93 secured at its opposite end to the armature I94 of anelectro-maenet I95 for a purpose to be described later. i

A pinion I96 secured on the shaft I9I at all times meshes with a pinionI91 secured on one end of the shaft I98 connected with a worm I99meshing with a toothed sector 200 rotatable on the shaft I33 of thelever I34. The sector gear 208 has provided thereon a contact plate 20!connected through a wire 202 with one of the terminals of a source ofcurrent, the opposite terminal of which is through a conductor 203connected with a conductive lever I34 through the winding of theelectro-magnet I95.

The shaft I9I on the end thereon adjacent to the bearing I92 has securedthereon a friction wheel 294, the periphery of which is adapted toselectively engage either a hub member 285 secured on the shaft I13 or ahub member 206 secured on a shaft 201 journalled at both ends thereon inapertures formed in the flanges I14 and I89. The shaft 201 is rigid witha gear 208 meshing with the gear I12 secured on the shaft I13 and itwill thus be seen that the hubs 205 and 206 are rotated in reversedirection from each other.

The above described device operates as follows:

When the pivotal lever I34, the angular displacements of which are afunction of P is not in contact engagement with the contact plate 20I,the energizing circuit for the magnet I95 is opened, the armature I94 isreturned to its rest condition and shifts the bearing I92 upwards thusbringing the friction wheel 284 into contact with the hub member 205.The shaft I M is then rotated and rotates the screw I88 which shifts thenut I81 and consequently the roller I towards the left as shown in thefigure. At the same time, the shaft I9I rotates the vertical shaft I98and the worm I99 in such direction that said worm I99 will rotate thegear sector200 in a direction to bring the contact plate 29! intoengagement with the lever I 34.

As soon as such contact has beenmade, the energizing circuit for themagnet I is completed and the armature I94 is attracted. Said armatureshifts the bearing I92 downwards and brings the friction wheel 204 incontact with the hub member 295. The shaft I9I is then rotated inreverse direction and drives the screw E88 in a direction to cause arightward displacement of the roller I80 as shown in the drawing.Concurrently, the shaft I9I rotates the vertical shaft I98 and the wormI99 in a direction such that the gear sector 200 willberotated to breakthe contact between the contact plate 20E and the lever I34.

It wil be seen that at any instant, the position of the roller-I80 alongthe cam I16 is conasemeo "i 'ditioned by the inclination of the leverI34 which in turn is function of Provided the profile of the cam I16issuitably predetermined, it will be seen that the angular speed of theroller I65 and therefore that of the shaft I50 will be proportional withFigs; 4 and 5 illustrate such a device. In the device diagrammaticalyshown in Fig. 4, similar reference numerals followed by the letter ahave been used to designate similar elements as in the device of Fig. 3and this device will not be described anew. However, in the device shownin Fig. 4, the shaft I8I which has slidably keyed thereon the rollerIBM, carries the pulse generating rotary switch. Moreover, in thisdevice, the inclination of the lever I34a is at each instant a functionof and this feature is obtained in the manner now to be described inreference with Fig. 5.

According to this figure which is essentially diagrammatic in character,a plate 2H1 is guided by means of rollers Ell to 2M and itsdisplacements are constantly proportional with the variations in theabsolute temperature 'I because one of its ends is connected with athermostatic strip ,1

2I5 for instance, the deformation of whichis a function of the variationin temperature.

The plate 2 It has mounted thereon four rollers I 2I6 to ZIQ betweenwhich there is arranged a ruler 229 so as to be guided by said rollers,while being slidably perpendicularly to the direction of displacement ofthe plate. The ruler 220 is at one of its ends subjected to the actionof a finger 22I displaceabfe in response to the variations in themagnetiude P and which for this purpose, 1

may for instance be connected with the movable end wall of a manometercapsule 222. The ruler 229 at its opposite end terminates in a finger223 maintained in continual engagement with one arm 22B of a bell-cranklever bent at right angle and pivoted on a fixed axis 225. It will beseen that provided the initial setting is suitably made, the angle a bywhich the arm 22% of the lever is rocked with respect to its initialposition, corresponding to P=fi, will be given by the formula:

tan 01:;-

The opposite arm 222 of the bell-crank lever is plate 228 guided betweenfour rollers 229 to 232 in such a way that the longitudinaldisplacements of said plate 228 will be proportional with Upon the plate228 there are provided four rollers 233 to 236 serving to guide thedisplacements of a ruler 231 in a direction perpendicular to thedisplacement of the plate 228. The ruler 231 at one of its ends ismaintained in contact with a finger 238 movable as a function of thevariations in A, While at its opposite end the ruler 231 comprises afinger 239 adapted to engage the lever I34a, and it will be seen thatthe angle ,3 formed at any given instant by the lever I34a with itsinitial setting corresponding with A Il, will be defined by the formula:

In such conditions and as a result of a suitable contour provided forthe cam Il'fia, it will be understood that the angular rate of theroller a and of the shaft I8Ia carrying the timing switch ISEa, andconsequently the number of pulses generated will be a function of Itwill of course be understood that the invention is not restricted to theforms of embodiment specifically described and illustrated and thatmodifications may be made within the scope of the ensuing claims.

In particular the cams rather than being defined with regard to thesquare roots of the re# spective variables, may be determined with thecontour corresponding to any desired function of the ratio V of saidvariables.

What I claim is:

1. In a servo-anemometer of the type described for inducing a movementthe speed of which is in direct ratio with the air speed of an aircraft,a frame, drive means mounted on said frame, a rotatable shaft on saidframe, transmission means from said drive means to said shaft, means formaintaining the speed of said shaft constants; cam of revolution securedon said shaft and the generatrix of which is a curve representative of afunction of AZ P a support movable with respect to said frame, a secondshaft on said movable support parallel with said first shaft androtatable at a speed vin direct ratio to the air speed of the aircraft,a rotatable member movable parallel with'said first rotatable shaft,supported on and drivingly con-I nected with said second shaft andadapted to remain tangent with the surface of said cam, resilient meansurging the support and thereby said movable member against said cam, andmeans for moving said movable member as a function of the current valueof 2. In a servo-anemometer of the type described at all times appliedagainst the end of a movable 7:5 fo du i g a m v m h sp d of wh sindirect ratio with the air speed of an aircraft, a frame, drive meansmounted on said frame, a rotatable shaft on said frame, transmissionmeans from said drive means to said shaft, means for maintaining thespeed. of said shaft constant, a cam of revolution secured on said shaftand the generatrix of which is a curve representative of a function ofA' l P a support movable with respect to said frame, a

second shaft on said movable support and parallel with said first shaftand rotatable at a speed in direct ratio to the air speed of theaircraft,

a rotatable member movable parallel with said first rotatable shaft,supported on and drivingly connected with said second shaft. and adaptedto remain tangent with the surface of said cam, resilient means urgingthe support and thereby said movable member against said cam, means formoving said movable member as a function of the current value of aperiodic electric switch on said second shaft, and electric circuitmeans connected with said switch.

3. A servo-anemometer as in claim 1, wherein the means for moving themovable member as a function of the current value of the movements ofsaid first slide block, a second slide block continuously in contactwith the free end of said barometer capsule and movable therebyperpendicularly to said first slide block, guide means for said secondslide block on said first slide block, a right-angle bell-crank leverpivoted on said frame having one arm in contact with said second slideblock, a third slide block, adapted to move parallel with said firstslide block and at all times in contact with the other arm of said bellcrank lever, guide means for said third slide block, means responsive tothe variations in A having one end rigid with the frame and the otherend movable perpendicularly to said third slide block, a fourth slideblock at all times in contact with the movable end of said A responsivemeans and movable perpendicularly with said third slide block, guidemeans for said fourth slide block on said third slide block, a leverpivoted on said frame and engaging said fourth slide block and meansconnecting said movable member with said lever, the positions of whichrepresent the current value of l' P EUGENE FRANQ DIS GILBERT GARNIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,354,832 Jung Oct. 5, 19202,251,498 Schwein Aug. 5, 1941 FOREIGN PATENTS Number Country Date374,730 Germany Apr. 2'7, 1923 193,452 Great Britain Feb. 26, 1923

